Asbestos Bodies and Non-asbestos Ferruginous Bodies
Biopersistent mineral fibers deposited in the lower respiratory tract that measure 15–20 microns or greater in length are taken up by alveolar macrophages. In a process referred to as frustrated phagocytosis, these macrophages coat the fibers with an iron protein matrix resulting in a golden brown, beaded, lancet, or dumbbell-shaped structure visible with light microscopy and referred to as a ferruginous body. When the fibrous core is asbestos, the structure is referred to as an asbestos body. The concentration of asbestos bodies in lung tissue correlates very well with the concentration of commercial amphibole fibers, amosite, or crocidolite. Chrysotile fibers form asbestos bodies less frequently, probably because these fibers are less biopersistent than the amphiboles and tend to break down into smaller fibers. Other fibers that form ferruginous bodies can be distinguished from true asbestos bodies morphologically; although erionite and refractory ceramic fiber ferruginous bodies are indistinguishable from true asbestos bodies by light microscopy.
